1. Field of the Invention
The invention is directed generally to semiconductors and more specifically to a semiconductor component for overvoltage protection of semiconductor components controllable by field effect having a freewheeling diode connected thereto, and having a voltage-limiting diode connected between the collector (drain) terminal and the gate terminal.
2. Description of the Related Art
Such a circuit arrangement has been described, for example, in the article "SMART-Power-Bauelemente auf der Basis der SIPMOS-Technologie", Elektronik 1987, Special Number Stromversorgungen, pp. 39-42, particularly FIG. 3. This figure has been reproduced as FIG. 4 of the present application. FIG. 4 shows an IGBT 1 having a freewheeling diode 4 connected between the collector terminal and the emitter terminal. The cathode terminal of the freewheeling diode 4 is connected to the collector terminal and the anode is connected to the emitter of the IGBT 1. In addition, a cathode terminal of a limiting diode 2 is connected to the collector terminal and its anode terminal is connected to the gate terminal of the IGBT 1 via a diode 3. The anode of the diode 3 is connected to the anode of limiting diode 2.
When an inductive load is shut off, a high voltage occurs at the IGBT 1 and, thus, at the freewheeling diode 4. In order to preclude jeopardizing the components, the IGBT 1 is switched slightly conductive via the limiting diode 2 and the diode 3 in case of an overvoltage. The shutoff speed is thus reduced and the over-voltage generated upon shut-off is correspondingly reduced.
For the described protective effect, the breakdown voltage of the limiting diode 2 must always lie below the breakdown voltage of the freewheeling diode 4 by a defined voltage. Since these voltages are temperature-dependent and the diodes are traversed by highly different currents, and thus, are warmed to different degrees, the spacing between the two breakdown voltages is not always maintained.